n amount of these substances, we know, is
absolutely necessary to carry on the work in the body, but harm comes
when a surplus is retained in excess of that which can be used in
performing the various processes. Consequently the function of the
kidneys to adjust the salts balance is by no means their least
important one.

~Elimination of the Toxins.~--The toxic substances manufactured in the
body and those resulting from bacterial action upon unabsorbed
proteins are likewise eliminated in the urine. Thus it can be readily
understood how necessary it is to keep these organs in good repair,
that they may continue their work in an efficient manner.

It is necessary from a pathological standpoint for the nurse to
understand the making of some of the simpler tests, that she may
simplify her own work and that of the physician.

~Excretion of Carbon Dioxide and Water.~--We have already spoken of
the combinations of carbon and hydrogen compounds. These substances
being oxidized, the carbon dioxide produced is eliminated by way of
the lungs and the water is excreted partly by way of the lungs and
skin, but chiefly by way of the kidneys.

~Oxidation and Excretion of Nitrogenous Substances.~--When the
nitrogenous substances are oxidized, the used-up oxygen products are
eliminated by the kidneys in the form of urea and more or less highly
oxidized substances, such as ammonia and other salts, purin bases, and
creatinin.

~Uric Acid~, the chief of the oxidation products of nucleoproteins, is
produced in the body and from food, and is always in the urine, being
one of its normal constituents. It is only when this substance is in
excess in the urine that a pathological condition is indicated.

~Examination of the Urine~, then, is made for several different
purposes: (1) to ascertain whether the kidneys are doing their work
properly; (2) to find if the kidneys, or any part of the urinary
tract, are either temporarily or permanently diseased; (3) to be able
to judge from the various substances in the urine whether there is any
abnormal process taking place in the body.

~Tests.~--In the examination of the urine for the above purposes,
certain definite tests are made. These tests differentiate between the
abnormal and the normal.

(1) Color.

(2) Amount in twenty-four hours.

(3) Odor.

(4) Specific gravity.

(5) Reaction, acid or alkaline.

(6) Albumen, indican, acetone bodies.

(7) Sugar.

(8) Microscopic examinati